Exercise intolerance in patients with heart failure and preserved left ventricular systolic function: failure of the Frank-Starling mechanism

Effects of Exercise Training on Cardiac Function in Heart Failure with Preserved Ejection Fraction

Nearly half of patients with heart failure in the community have heart failure with preserved ejection fraction (HFpEF). Patients with HFpEF are often elderly and their primary chronic symptom is severe exercise intolerance. Left ventricular diastolic dysfunction is associated with the pathophysiology of HFpEF and is an important contributor to exercise intolerance in HFpEF patients. The effects of exercise training on left ventricular diastolic function in HFpEF patients have been examined in several randomised clinical trials. Meta-analysis of the trials indicates that exercise training can provide clinically relevant improvements in exercise capacity without significant change in left ventricular structure or function in HFpEF patients. Further studies are necessary to elucidate the exact mechanisms of exercise intolerance in HFpEF patients and to develop recommendations regarding the most effective type, intensity, frequency, and duration of training in this group.

Exercise Intolerance in Heart Failure: Central Role for the Pulmonary System

We propose that abnormalities of the pulmonary system contribute significantly to the exertional dyspnea and exercise intolerance observed in patients with chronic heart failure. Interventions designed to address the deleterious pulmonary manifestations of heart failure may, therefore, yield promising improvements in exercise tolerance in this population.

Value of combined cardiopulmonary and echocardiography stress test to characterize the haemodynamic and metabolic responses of patients with heart failure and mid-range ejection fraction

AIMS

To characterize heart failure (HF) with mid-range ejection fraction (HFmrEF), combining cardiopulmonary exercise test, and exercise stress echocardiography.

METHODS AND RESULTS

We studied 169 consecutive subjects (age 62.3 ± 11 years; 74% male): 30 healthy controls, 45 patients with HF and preserved EF (HFpEF), 40 HFmrEF, and 54 with HF and reduced EF (HFrEF). Left ventricular (LV) stroke volume (SV), EF, elastance, global longitudinal strain, E/E', oxygen consumption (VO2), and arterial-venous oxygen content difference (AVO2diff) were measured in all exercise stages. HFmrEF revealed baseline features intermediate between HFrEF and HFpEF, except for B-type natriuretic peptide levels, which was similar to HFpEF and significantly lower than HFrEF. Peak VO2 was not significantly different between HF groups. HFrEF exhibited a significantly lower peak SV as compared to either HFpEF or HFmrEF (74.3 ± 21.8 mL vs. 88.0 ± 17.4 mL and 96.5 ± 25.1 mL; P < 0.01), whereas peak heart rate was not significantly different between HF groups. A significantly reduced AVO2diff at peak exercise was apparent in HFpEF and HFmrEF (15.2 ± 3.3 mL/dL and 13.3 ± 4.2 mL/dL) vs. HFrEF (17.±6.6 mL/dL; P < 0.01), whereas no significant difference was reported between HFpEF and HFmrEF. Multivariate analysis in the overall population and all groups revealed peak parameters as independent predictors of peak VO2 (R2 = 0.90, P < 0.0001); AVO2diff showed the largest standardized regression coefficient.

CONCLUSION

In HFpEF and HFmrEF, effort intolerance is predominantly due to peripheral factors (AVO2diff), whereas in HFrEF peak VO2 is restricted by low increases in SV. Individual therapy according to which component of VO2 is more impaired is advisable.

Left ventricular concentric remodeling and impaired cardiorespiratory fitness in patients with heart failure and preserved ejection fraction

BACKGROUND

Left ventricular (LV) concentric remodeling refers to a process by which increased LV relative wall thickness alters myocardial geometry, resulting in reduced LV end-diastolic volume (LVEDV) and stroke volume (SV). While the degree of concentric remodeling is a negative prognostic factor in heart failure with preserved ejection fraction (HFpEF), it is not known how it contributes to cardiorespiratory fitness (CRF).

METHODS

We performed a retrospective analysis of patients with HFpEF who underwent treadmill single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) and cardiopulmonary exercise testing (CPX). From exercise SPECT-MPI, we recorded postexercise LVEDVi, LVESVi, SVi, LVEF, the presence and extent of perfusion defects, and perfusion reversibility. Peak oxygen consumption (VO<inf>2</inf>), the oxygen uptake efficiency slope (OUES), oxygen (O<inf>2</inf>) pulse, ventilatory efficiency (V<inf>E</inf>/VCO<inf>2</inf> slope), ventilatory anaerobic threshold, respiratory exchange ratio, exercise time, and maximum heart rate were obtained from CPX. Data are expressed as mean (±standard deviation). Univariate and multivariate linear regression was performed.

RESULTS

We identified 23 subjects who had completed both an exercise SPECT-MPI and a CPX. Patients were more commonly women (83%), black (65%), middle age (50 [±7.3] years), and obese (Body Mass Index [BMI] 39.7 [±6.0] kg/m²). Greater LVEDVi and LVESVi correlated positively with peak VO<inf>2</inf> (R=+0.648, P=0.001; R=+0.601, P=0.002), O<inf>2</inf> pulse (R=+0.686, P<0.001; R=+0.625, P=0.001) and OUES (R=+0.882, P<0.001; R=+0.779, P<0.001). The LVEF correlated inversely with peak VO<inf>2</inf> and OUES (R=-0.450, P=0.031; R=-0.485, P=0.035). Perfusion defect area, grade of severity, and presence of reversibility were not associated with CRF variables.

CONCLUSIONS

Postexercise reduced LV volumes correlate with measures of impaired CRF in patients with HFpEF, thus supporting a pathophysiologic role of concentric remodeling in impaired CRF in HFpEF.

Understanding preload and preload reserve within the conceptual framework of a limited range of possible left ventricular end-diastolic volumes

Preload has been variously defined, but if there is to be a direct relationship with activity of the Frank-Starling mechanism in its action to increase the force and extent of contraction, preload must directly reflect myocardial stretch. The Frank-Starling mechanism is activated during any stretch of a cardiac chamber beyond its resting size, which is present immediately before contraction. Every left ventricle has an intrinsic and limited range of possible volumes at end diastole. There is a curvilinear relationship between left ventricular (LV) end-diastolic pressure (LVEDP) and LV end-diastolic volume (LVEDV), and, at maximal or near maximal LVEDV, there will be a high LVEDP. Within the possible range, the LVEDV will be determined by the extent of filling, any change in LVEDV will result in changed activity of the Frank-Starling mechanism, and change in LVEDV might, therefore, be considered to represent change in preload. On the other hand, it is the difference between the current and the maximal possible LVEDV (or the preload reserve) that may be of the most clinical relevance. There is a reciprocal relationship between preload and preload reserve, with minor or absent LV preload reserve indicating that there will be either minimal or no increase in stroke volume following intravenous fluid administration. As left atrial pressure can remain within the normal range when the LVEDP is elevated, it is LVEDP, and not left atrial pressure, that provides the most reliable guide to preload reserve in an individual at a specific period in time.

Detrended fluctuation analysis can detect the impairment of heart rate regulation in patients with heart failure with preserved ejection fraction

BACKGROUND

The impairment of short-term heart rate regulation in patients with heart failure with preserved ejection fraction (HFpEF) can cause acute hemodynamic collapse. Detrended fluctuation analysis (DFA) is a useful tool for the diagnosis of heart diseases and the prediction of mortality. In DFA, the short-term scaling exponent α is decreased in heart failure. However, its change in HFpEF patients remains unclear.

METHODS

Twenty patients diagnosed with HFpEF [defined as brain natriuretic peptide (BNP) >100 pg/mL, ejection fraction (EF) ≥50%, and without significant valvular disease], 20 diagnosed with non-HFpEF (BNP > 100 pg/mL and EF < 50%), and 20 control subjects generally matched for age and gender were enrolled. Holter electrocardiography was performed, and heart rate variability was calculated. In the DFA, the scaling exponents in 1000 beats were calculated for each 15-min segment and the average of all segments was used. We compared both the short-term (<11 beats, α1) and long-term (≥11 beats, α2) scaling exponents among the three groups.

RESULTS

In the HFpEF, non-HFpEF, and control groups, α1 was 0.73 ± 0.27, 0.66 ± 0.29, and 1.01 ± 0.20 (p < 0.01), and α2 was 0.95 ± 0.08, 0.88 ± 0.11, and 0.96 ± 0.07 (p < 0.01), respectively. The α1 exponent was significantly decreased in the HFpEF group (p < 0.01 vs. control) and the non-HFpEF group (p < 0.01 vs. control), while the α2 exponent was significantly decreased in the non-HFpEF group only (p < 0.05 vs. HFpEF and control).

CONCLUSIONS

Short-term heart rate regulation is impaired in patients with HFpEF, while patients with non-HFpEF have both short-term and long-term impairment.

Diastolic Ventricular Interaction in Heart Failure With Preserved Ejection Fraction

Background

Exercise‐induced pulmonary hypertension is common in heart failure with preserved ejection fraction (HFpEF). We hypothesized that this could result in pericardial constraint and diastolic ventricular interaction in some patients during exercise.

Methods and Results

Contrast stress echocardiography was performed in 30 HFpEF patients, 17 hypertensive controls, and 17 normotensive controls (healthy). Cardiac volumes, and normalized radius of curvature (NRC) of the interventricular septum at end‐diastole and end‐systole, were measured at rest and peak‐exercise, and compared between the groups. The septum was circular at rest in all 3 groups at end‐diastole. At peak‐exercise, end‐systolic NRC increased to 1.47±0.05 (P<0.001) in HFpEF patients, confirming development of pulmonary hypertension. End‐diastolic NRC also increased to 1.54±0.07 (P<0.001) in HFpEF patients, indicating septal flattening, and this correlated significantly with end‐systolic NRC (ρ=0.51, P=0.007). In hypertensive controls and healthy controls, peak‐exercise end‐systolic NRC increased, but this was significantly less than observed in HFpEF patients (HFpEF, P=0.02 versus hypertensive controls; P<0.001 versus healthy). There were also small, non‐significant increases in end‐diastolic NRC in both groups (hypertensive controls, +0.17±0.05, P=0.38; healthy, +0.06±0.03, P=0.93). In HFpEF patients, peak‐exercise end‐diastolic NRC also negatively correlated (r=−0.40, P<0.05) with the change in left ventricular end‐diastolic volume with exercise (ie, the Frank‐Starling mechanism), and a trend was noted towards a negative correlation with change in stroke volume (r=−0.36, P=0.08).

Conclusions

Exercise pulmonary hypertension causes substantial diastolic ventricular interaction on exercise in some patients with HFpEF, and this restriction to left ventricular filling by the right ventricle exacerbates the pre‐existing impaired Frank‐Starling response in these patients.

Heart Failure With Preserved Ejection Fraction: A Comprehensive Review and Update of Diagnosis, Pathophysiology, Treatment, and Perioperative Implications

Almost three-quarters of all heart failure patients who are older than 65 have heart failure with preserved ejection fraction (HFpEF). The proportion and hospitalization rate of patients with HFpEF are increasing steadily relative to patients in whom heart failure occurs as result of reduced ejection fraction. The predominance of the HFpEF phenotype most likely is explained by the prevalence of medical conditions associated with an aging population. A multitude of age-related, medical, and lifestyle risk factors for HFpEF have been identified as potential causes for the sustained low-grade proinflammatory state that accelerates disease progression. Profound left ventricular (LV) systolic and diastolic stiffening, elevated LV filling pressures, reduced arterial compliance, left atrial hypertension, pulmonary venous congestion, and microvascular dysfunction characterize HFpEF, but pulmonary arterial hypertension, right ventricular dilation and dysfunction, and atrial fibrillation also frequently occur. These cardiovascular features make patients with HFpEF exquisitely sensitive to the development of hypotension in response to acute declines in LV preload or afterload that may occur during or after surgery. With the exception of symptom mitigation, lifestyle modifications, and rigorous control of comorbid conditions, few long-term treatment options exist for these unfortunate individuals. Patients with HFpEF present for surgery on a regular basis, and anesthesiologists need to be familiar with this heterogeneous and complex clinical syndrome to provide successful care. In this article, the authors review the diagnosis, pathophysiology, and treatment of HFpEF and also discuss its perioperative implications.

Beyond the myocardium? SGLT2 inhibitors target peripheral components of reduced oxygen flux in the diabetic patient with heart failure with preserved ejection fraction

Recent cardiovascular outcome trials have highlighted the propensity of the antidiabetic agents, SGLT2 inhibitors (SGLT2is or -flozin drugs), to exert positive clinical outcomes in patients with cardiovascular disease at risk for major adverse cardiovascular events (MACEs). Of interest in cardiac diabetology is the physiological status of the patient with T2DM and heart failure with preserved ejection fraction (HFpEF), a well-examined association. Underlying this pathologic tandem are the effects that long-standing hyperglycemia has on the ability of the HFpEF heart to adequately deliver oxygen. It is believed that shortcomings in oxygen diffusion or utilization and the resulting hypoxia thereafter may play a role in underlying the clinical sequelae of patients with T2DM and HFpEF, with implications in the long-term decline of extra-cardiac tissue. Oxygen consumption is one of the most critical factors in indexing heart failure disease burden, warranting a probe into the role of SGLT2i on oxygen utility in HFpEF and T2DM. We investigated the role of oxygen flux in the patient with T2DM and HFpEF extending beyond the heart with focuses on cellular metabolism, perivascular fibrosis with endothelial dysfunction, hematologic changes, and renal effects with neurohormonal considerations in the patient with HFpEF and T2DM. Moreover, we give a commentary on potential therapeutic targets of these components with SGLT2i to gain insight into disease burden amelioration in patients with HFpEF and T2DM.

Association between the tissue accumulation of advanced glycation end products and exercise capacity in cardiac rehabilitation patients

Background

Advanced glycation end products (AGEs) are associated with aging, diabetes mellitus (DM), and other chronic diseases. Recently, the accumulation of AGEs can be evaluated by skin autofluorescence (SAF). However, the relationship between SAF levels and exercise capacity in patients with cardiovascular disease (CVD) remains unclear. This study aimed to investigate the association between the tissue accumulation of AGEs and clinical characteristics, including exercise capacity, in patients with CVD.

Methods

We enrolled 319 consecutive CVD patients aged ≥40 years who underwent early phase II cardiac rehabilitation (CR) at our university hospital between November 2015 and September 2017. Patient background, clinical data, and the accumulation of AGEs assessed by SAF were recorded at the beginning of CR. Characteristics were compared between two patient groups divided according to the median SAF level (High SAF and Low SAF).

Results

The High SAF group was significantly older and exhibited a higher prevalence of DM than the Low SAF group. The sex ratio did not differ between the two groups. AGE levels showed significant negative correlations with peak oxygen uptake and ventilator efficiency (both P <  0.0001). Exercise capacity was significantly lower in the high SAF group than in the low SAF group, regardless of the presence or absence of DM (P <  0.05). A multivariate logistic regression analysis showed that SAF level was an independent factor associated with reduced exercise capacity (odds ratio 2.10; 95% confidence interval 1.13–4.05; P = 0.02).

Conclusion

High levels of tissue accumulated AGEs, as assessed by SAF, were significantly and independently associated with reduced exercise capacity. These data suggest that measuring the tissue accumulation of AGEs may be useful in patients who have undergone CR, irrespective of whether they have DM.

Association of Intensive Lifestyle Intervention, Fitness, and Body Mass Index With Risk of Heart Failure in Overweight or Obese Adults With Type 2 Diabetes Mellitus: An Analysis From the Look AHEAD Trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with a higher risk for heart failure (HF). The impact of a lifestyle intervention and changes in cardiorespiratory fitness (CRF) and body mass index on risk for HF is not well established.

METHODS

Participants from the Look AHEAD trial (Action for Health in Diabetes) without prevalent HF were included. Time-to-event analyses were used to compare the risk of incident HF between the intensive lifestyle intervention and diabetes support and education groups. The associations of baseline measures of CRF estimated from a maximal treadmill test, body mass index, and longitudinal changes in these parameters with risk of HF were evaluated with multivariable adjusted Cox models.

RESULTS

Among the 5109 trial participants, there was no significant difference in the risk of incident HF (n=257) between the intensive lifestyle intervention and the diabetes support and education groups (hazard ratio, 0.96 [95% CI, 0.75-1.23]) over a median follow-up of 12.4 years. In the most adjusted Cox models, the risk of HF was 39% and 62% lower among moderate fit (tertile 2: hazard ratio, 0.61 [95% CI, 0.44-0.83]) and high fit (tertile 3: hazard ratio, 0.38 [95% CI, 0.24-0.59]) groups, respectively (referent group: low fit, tertile 1). Among HF subtypes, after adjustment for traditional cardiovascular risk factors and interval incidence of myocardial infarction, baseline CRF was not significantly associated with risk of incident HF with reduced ejection fraction. In contrast, the risk of incident HF with preserved ejection fraction was 40% lower in the moderate fit group and 77% lower in the high fit group. Baseline body mass index also was not associated with risk of incident HF, HF with preserved ejection fraction, or HF with reduced ejection fraction after adjustment for CRF and traditional cardiovascular risk factors. Among participants with repeat CRF assessments (n=3902), improvements in CRF and weight loss over a 4-year follow-up were significantly associated with lower risk of HF (hazard ratio per 10% increase in CRF, 0.90 [95% CI, 0.82-0.99]; per 10% decrease in body mass index, 0.80 [95% CI, 0.69-0.94]).

CONCLUSIONS

Among participants with type 2 diabetes mellitus in the Look AHEAD trial, the intensive lifestyle intervention did not appear to modify the risk of HF. Higher baseline CRF and sustained improvements in CRF and weight loss were associated with lower risk of HF. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00017953.

Effects of exercise training on cardiac function, exercise capacity, and quality of life in heart failure with preserved ejection fraction: a meta-analysis of randomized controlled trials

Left ventricular (LV) diastolic dysfunction is associated with the pathophysiology of heart failure with preserved ejection fraction (HFpEF) and contributes importantly to exercise intolerance that results in a reduced quality of life (QOL) in HFpEF patients. Although the effects of exercise training on LV diastolic function, exercise capacity, or QOL in HFpEF patients have been examined in randomized clinical trials (RCTs), results are inconsistent due partly to limited power with small sample sizes. We aimed to conduct a meta-analysis of RCTs examining the effects of exercise training on LV diastolic function and exercise capacity as well as QOL in HFpEF patients. The search of electronic databases identified 8 RCTs with 436 patients. The duration of exercise training ranged from 12 to 24 weeks. In the pooled analysis, exercise training improved peak exercise oxygen uptake (weighted mean difference [95% CI], 1.660 [0.973, 2.348] ml/min/kg), 6-min walk distance (33.883 [12.384 55.381] m), and Minnesota Living With Heart Failure Questionnaire total score (9.059 [3.083, 15.035] point) compared with control. In contrast, exercise training did not significantly change early diastolic mitral annular velocity (weighted mean difference [95% CI], 0.317 [- 0.952, 1.587] cm/s), the ratio of early diastolic mitral inflow to annular velocities (- 1.203 [- 4.065, 1.658]), or LV ejection fraction (0.850 [- 0.128, 1.828] %) compared with control. In conclusion, the present meta-analysis suggests that exercise training improves exercise capacity and QOL without significant change in LV systolic or diastolic function in HFpEF patients.

How to diagnose heart failure with preserved ejection fraction: the HFA-PEFF diagnostic algorithm: a consensus recommendation from the Heart Failure Association (HFA) of the European Society of Cardiology (ESC)

Making a firm diagnosis of chronic heart failure with preserved ejection fraction (HFpEF) remains a challenge. We recommend a new stepwise diagnostic process, the 'HFA-PEFF diagnostic algorithm'. Step 1 (P=Pre-test assessment) is typically performed in the ambulatory setting and includes assessment for heart failure symptoms and signs, typical clinical demographics (obesity, hypertension, diabetes mellitus, elderly, atrial fibrillation), and diagnostic laboratory tests, electrocardiogram, and echocardiography. In the absence of overt non-cardiac causes of breathlessness, HFpEF can be suspected if there is a normal left ventricular (LV) ejection fraction, no significant heart valve disease or cardiac ischaemia, and at least one typical risk factor. Elevated natriuretic peptides support, but normal levels do not exclude a diagnosis of HFpEF. The second step (E: Echocardiography and Natriuretic Peptide Score) requires comprehensive echocardiography and is typically performed by a cardiologist. Measures include mitral annular early diastolic velocity (e'), LV filling pressure estimated using E/e', left atrial volume index, LV mass index, LV relative wall thickness, tricuspid regurgitation velocity, LV global longitudinal systolic strain, and serum natriuretic peptide levels. Major (2 points) and Minor (1 point) criteria were defined from these measures. A score ≥5 points implies definite HFpEF; ≤1 point makes HFpEF unlikely. An intermediate score (2-4 points) implies diagnostic uncertainty, in which case Step 3 (F₁ : Functional testing) is recommended with echocardiographic or invasive haemodynamic exercise stress tests. Step 4 (F₂ : Final aetiology) is recommended to establish a possible specific cause of HFpEF or alternative explanations. Further research is needed for a better classification of HFpEF.

Association between bisoprolol plasma concentration and worsening of heart failure: (CVI ARO 6)

BACKGROUND

Although bisoprolol has been established to prevent heart failure (HF), finding the optimal dose remains a challenge. It is crucial to understand the distribution of bisoprolol plasma concentration (Bis-PC) and association with outcomes.

METHODS

This was a single-center observational study in 114 HF patients under once-daily bisoprolol. After obtaining trough Bis-PC, patients were followed-up for 1 year. The primary endpoint was worsening of HF. Patients were divided according to the tertiles of Bis-PC.

RESULTS

In multivariate logistic regression analysis, independent predictors of high Bis-PC (1st tertile: ≥ 5.38 ng/mL) were age, eGFR, and bisoprolol dose. The cumulative incidence rates of the primary endpoint were 10.5%/13.2%/26.3% in low/middle/high Bis-PC categories, respectively (log rank test, p = 0.087). Bis-PC was independently associated with the primary endpoint (hazard ratio [HR], 1.19 [per ng/mL], 95% CI 1.03-1.36). In subgroups, high Bis-PC was independently associated with the primary endpoint in elderly (HR 6.32, 95% CI 1.34-29.83) and HF with preserved ejection fraction (HFpEF) (HR 3.52, 95% CI 1.06-11.70).

CONCLUSIONS

Bis-PC was increased by age and renal dysfunction, and high Bis-PC was associated with worsening of HF in elderly and HFpEF patients. Care should be taken to avoid overdose.

Mitochondrial Dysfunction in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome with an increasingly recognized heterogeneity in pathophysiology. Exercise intolerance is the hallmark of HFpEF and appears to be caused by both cardiac and peripheral abnormalities in the arterial tree and skeletal muscle. Mitochondrial abnormalities can significantly contribute to impaired oxygen utilization and the resulting exercise intolerance in HFpEF. We review key aspects of the complex biology of this organelle, the clinical relevance of mitochondrial function, the methods that are currently available to assess mitochondrial function in humans, and the evidence supporting a role for mitochondrial dysfunction in the pathophysiology of HFpEF. We also discuss the role of mitochondrial function as a therapeutic target, some key considerations for the design of early-phase clinical trials using agents that specifically target mitochondrial function to improve symptoms in patients with HFpEF, and ongoing trials with mitochondrial agents in HFpEF.

Stress Echocardiography-Derived E/e' Predicts Abnormal Exercise Hemodynamics in Heart Failure With Preserved Ejection Fraction

Background

The correlation between echocardiographic parameters and hemodynamics data in patients with heart failure with preserved ejection fraction (HFpEF) is unclear. It is important to find a non-invasive echocardiographic parameter for predicting exercise pulmonary capillary wedge pressure (PCWP).

Aim

This study sought to determine the correlation between echocardiographic parameters and hemodynamics data at rest and during exercise in HFpEF patients.

Methods and Results

This study was a cross-sectional cohort exploratory analysis of baseline data from the ILO-HOPE trial. A total of 34 HFpEF patients were enrolled. The average age was 70 ± 12 years, and most (74%) were women. The patients underwent invasive cardiac catheterization and expired gas analysis at rest and during exercise. Echocardiography including tissue Doppler imaging was performed, and global longitudinal strain and other novel diastolic function indexes were analyzed at rest and during exercise. At rest, no significant correlation was noted between resting PCWP and echocardiographic parameters. However, a significant correlation was observed between post-exercise PCWP and stress E/e′ (septal, lateral, and mean) ratio (p = 0.003, 0.031, 0.012). Moreover, post-exercise ΔPCWP showed a good correlation with stress E/e′ (septal, lateral, and mean; all p ≤ 0.001) and global longitudinal strain (GLS) during exercise (p = 0.03). After multivariate regression analysis with adjustment for possible confounding factors including age and sex, there was still a significant correlation between post-exercise ΔPCWP and E/e′ (r = 0.62, p < 0.001 for E/e′_mean).

Conclusion

Only stress echocardiography derived tissue Doppler E/e′ ratio is closely correlated with abnormal exercise hemodynamics (PCWP and post-exercise ΔPCWP) in HFpEF. This echocardiographic marker is substantially more sensitive than other novel echocardiographic parameters during exercise, and may have significant diagnostic utility for ambulatory HFpEF patients with dyspnea.

Clinical Trial Registration

https://www.clinicaltrials.gov, identifier NCT03620526.

Simultaneous determination of dynamic cardiac metabolism and function using PET/MRI

BACKGROUND

Cardiac metabolic changes in heart disease precede overt contractile dysfunction. However, metabolism and function are not typically assessed together in clinical practice. The purpose of this study was to develop a cardiac positron emission tomography/magnetic resonance (PET/MR) stress test to assess the dynamic relationship between contractile function and metabolism in a preclinical model.

METHODS

Following an overnight fast, healthy pigs (45-50 kg) were anesthetized and mechanically ventilated. 18F-fluorodeoxyglucose (18F-FDG) solution was administered intravenously at a constant rate of 0.01 mL/s for 60 minutes. A cardiac PET/MR stress test was performed using normoxic gas (FIO2 = .209) and hypoxic gas (FIO2 = .12). Simultaneous cardiac imaging was performed on an integrated 3T PET/MR scanner.

RESULTS

Hypoxic stress induced a significant increase in heart rate, cardiac output, left ventricular (LV) ejection fraction (EF), and peak torsion. There was a significant decline in arterial SpO2, LV end-diastolic and end-systolic volumes in hypoxia. Increased LV systolic function was coupled with an increase in myocardial FDG uptake (Ki) during hypoxic stress.

CONCLUSION

PET/MR with continuous FDG infusion captures dynamic changes in both cardiac metabolism and contractile function. This technique warrants evaluation in human cardiac disease for assessment of subtle functional and metabolic abnormalities.

The interactions between respiratory and cardiovascular systems in systolic heart failure

Heart failure (HF) is a complex and multifaceted disease. The disease affects multiple organ systems, including the respiratory system. This review provides three unique examples illustrating how the cardiovascular and respiratory systems interrelate because of the pathology of HF. Specifically, these examples outline the impact of HF pathophysiology on 1) respiratory mechanics and the mechanical "cost" of breathing; 2) mechanical interactions of the heart and lungs; and on 3) abnormalities of pulmonary gas exchange during exercise, and how this may be applied to treatment. The goal of this review is to, therefore, raise the awareness that HF, though primarily a disease of the heart, is accompanied by marked pathology of the respiratory system.

Relative Impairments in Hemodynamic Exercise Reserve Parameters in Heart Failure With Preserved Ejection Fraction: A Study-Level Pooled Analysis

OBJECTIVES

The aim of this study was to compare the relative impairment in different exercise hemodynamic reserve parameters in patients with heart failure with preserved ejection fraction (HFpEF) and control patients using a study-level meta-analysis.

BACKGROUND

A cardinal manifestation of chronic HFpEF is severely decreased exercise capacity. Developing effective therapies for exercise intolerance in HFpEF requires optimal understanding of the factors underlying exercise intolerance.

METHODS

Data were included from 17 unique cohorts that measured peak oxygen uptake and hemodynamic or echocardiographic parameters during exercise in patients with HFpEF and control subjects in this meta-analysis. Standardized mean differences (SMDs) in the exercise reserve (exercise - resting) measures of hemodynamic or echocardiographic parameters between the HFpEF and control groups were pooled in a random-effects meta-analysis.

RESULTS

The pooled analysis included 910 patients with HFpEF and 476 control subjects. In pooled analysis, patients with HFpEF had significantly lower peak oxygen uptake (SMD: -2.13; 95% confidence interval [CI]: -2.68 to -1.57). Among hemodynamic exercise reserve parameters, the largest impairment was observed in chronotropic response reserve (change in heart rate from rest to peak exercise; SMD: -1.87; 95% CI: -2.44 to -1.29), followed by exaggerated increase in pulmonary capillary wedge pressure with exercise (SMD: 1.78; 95% CI: 1.46 to 2.09). Significant abnormalities were also observed in the arteriovenous oxygen difference reserve and stroke volume reserve between the HFpEF and control groups.

CONCLUSIONS

The most consistent and severe hemodynamic reserve abnormalities observed in patients with HFpEF were impairment in chronotropic reserve and exaggerated increase in pulmonary capillary wedge pressure with exercise. These may be important targets for therapeutic strategies to improve exercise tolerance in patients with HFpEF.

Verification of Echocardiographic Assessment of Left Ventricular Diastolic Dysfunction in Patients With Preserved Left Ventricular Ejection Fraction Using the American Society of Echocardiography and European Association of Cardiovascular Imaging 2016 Recommendations

Background: Non-invasive evaluation of left ventricular (LV) diastolic dysfunction (DD) and elevated LV filling pressure are crucial for diagnosing heart failure. The 2016 American Society of Echocardiography/European Association of Cardiovascular Imaging (ASE/EACVI) recommendations for evaluating elevated LV filling pressure (algorithm B) have acceptable diagnostic accuracy, including in patients with reduced LV ejection fraction (EF). No prior study, however, has assessed the diagnostic accuracy of algorithm A of the ASE/EACVI recommendations for evaluating LVDD in patients with normal LVEF.

Methods and Results: We evaluated the clinical relevance of algorithm A in 94 patients who underwent invasive LV pressure measurement. Algorithm A identified invasively defined LVDD (time constant τ≥48 ms and/or LV end-diastolic pressure ≥16 mmHg) with low sensitivity (22.4%) but high specificity (90.7%). Algorithm A also identified elevated LV filling pressure with low sensitivity (41.7%) but high specificity (87.5%), and with a high negative predictive value (90.9%).

Conclusions: Algorithm A may not be useful for screening LVDD in patients with normal LVEF. Negative findings using algorithm A, however, may identify a patient with normal LVDD with high specificity, and most of such patients will have LV pre-A pressure in the normal range.

Myocardial Energetics in Heart Failure With Preserved Ejection Fraction

BACKGROUND

The role of coronary microvascular disease and its impact on functional and energetic reserve in heart failure with preserved ejection fraction (HFpEF) remains unclear. We hypothesized that in response to submaximal pharmacologic stress (dobutamine), patients with HFpEF have impairment in left ventricular (LV) myocardial mechanical (external work [EW]), energetic (myocardial O₂ consumption [MVO₂]), and myocardial blood flow (MBF) reserve. We further assessed whether coupling of MBF to EW is impaired in HFpEF and associated with compensatory increases or pathological decreases in myocardial O₂ extraction. Lastly, we assessed whether coupling of MVO₂ to EW (mechanical efficiency) was impaired in HFpEF.

METHODS AND RESULTS

In prospectively enrolled patients with HFpEF (n=19) and age/sex-matched healthy controls (n=19), we performed ¹¹C-acetate positron emission tomography assessing MVO₂ and MBF at rest and during dobutamine infusion. EW was calculated as stroke volume (echo)×end-systolic pressure×heart rate. At rest, compared with controls, patients with HFpEF had higher LV EW, MVO₂, and MBF. With dobutamine, LV EW, MVO₂, and MBF increased in both HFpEF and controls; however, the magnitude of increases was significantly smaller in HFpEF. In both groups, MBF increased in relation to EW, but in HFpEF, the slope of the relationship was significantly smaller than in controls. Myocardial O₂ extraction was increased in HFpEF. Mechanical efficiency was similar in HFpEF and controls. In a post hoc analysis, HFpEF patients with LV hypertrophy (n=10) had significant reductions in LV mechanical efficiency relative to controls.

CONCLUSIONS

In HFpEF during submaximal dobutamine stress, there is myocardial mechanical-, energetic- and flow-reserve dysfunction with impaired coupling of blood flow to demand and slight increases in myocardial O₂ extraction. These findings provide evidence that coronary microvascular dysfunction is present in HFpEF, limits O₂ supply relative to demand, and is associated with reserve dysfunction.

Impaired Exercise Tolerance in Heart Failure: Role of Skeletal Muscle Morphology and Function

PURPOSE OF REVIEW

To discuss the impact of deleterious changes in skeletal muscle morphology and function on exercise intolerance in patients with heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF), as well as the utility of exercise training and the potential of novel treatment strategies to preserve or improve skeletal muscle morphology and function.

RECENT FINDINGS

Both HFrEF and HFpEF patients exhibit a reduction in percent of type I (oxidative) muscle fibers and oxidative enzymes coupled with abnormal mitochondrial respiration. These skeletal muscle abnormalities contribute to impaired oxidative metabolism with an earlier shift towards glycolytic metabolism during exercise that is strongly associated with exercise intolerance. In both HFrEF and HFpEF patients, peripheral "non-cardiac" factors are important determinants of the improvement in exercise tolerance following aerobic exercise training. Adjunctive strategies that include nutritional supplementation with amino acids and/or anabolic drugs to stimulate anabolic molecular pathways in skeletal muscle show great promise for improving exercise tolerance and treating heart failure-associated sarcopenia, but these efforts remain early in their evolution, with no immediate clinical applications. There is consistent evidence that heart failure is associated with multiple skeletal muscle abnormalities which impair oxygen uptake and utilization and contribute greatly to exercise intolerance. Exercise training induces favorable adaptations in skeletal muscle morphology and function that contribute to improvements in exercise tolerance in patients with HFrEF. The contribution of skeletal muscle adaptations to improved exercise tolerance following exercise training in HFpEF remains unknown and warrants further investigation.

Left Ventricular Mass Change After Anthracycline Chemotherapy

BACKGROUND

Myocardial atrophy and left ventricular (LV) mass reductions are associated with fatigue and exercise intolerance. The relationships between the receipt of anthracycline-based chemotherapy (Anth-bC) and changes in LV mass and heart failure (HF) symptomatology are unknown, as is their relationship to LV ejection fraction (LVEF), a widely used measurement performed in surveillance strategies designed to avert symptomatic HF associated with cancer treatment.

METHODS AND RESULTS

We performed blinded, serial assessments of body weight, LVEF and mass, LV-arterial coupling, aortic stiffness, and Minnesota Living with Heart Failure Questionnaire measures before and 6 months after initiating Anth-bC (n=61) and non-Anth-bC (n=15), and in 24 cancer-free controls using paired t and χ² tests and multivariable linear models. Participants averaged 51±12 years, and 70% were women. Cancer diagnoses included breast cancer (53%), hematologic malignancy (42%), and soft tissue sarcoma (5%). We observed a 5% decline in both LVEF (P<0.0001) and LV mass (P=0.03) in the setting of increased aortic stiffness and disrupted ventricular-arterial coupling in those receiving Anth-bC but not other groups (P=0.11-0.92). A worsening of the Minnesota Living with Heart Failure Questionnaire score in Anth-bC recipients was associated with myocardial mass declines (r=-0.27; P<0.01) but not with LVEF declines (r=0.11; P=0.45). Moreover, this finding was independent of LVEF changes and body weight.

CONCLUSIONS

Early after Anth-bC, LV mass reductions associate with worsening HF symptomatology independent of LVEF. These data suggest an alternative mechanism whereby anthracyclines may contribute to HF symptomatology and raise the possibility that surveillance strategies during Anth-bC should also assess LV mass.

Impaired oxygen uptake kinetics in heart failure with preserved ejection fraction

Objective

The time needed to increase oxygen utilisation to meet metabolic demand (V̇O2 kinetics) is impaired in heart failure (HF) with reduced ejection fraction and is an independent risk factor for HF mortality. It is not known if V̇O2 kinetics are slowed in HF with preserved ejection fraction (HFpEF). We tested the hypothesis that V̇O2 kinetics are slowed during submaximal exercise in HFpEF and that slower V̇O2 kinetics are related to impaired peripheral oxygen extraction.

Methods

Eighteen HFpEF patients (68±7 years, 10 women) and 18 healthy controls (69±6 years, 10 women) completed submaximal and peak exercise testing. Cardiac output (acetylene rebreathing, Q̇c), ventilatory oxygen uptake (V̇O2, Douglas bags) and arterial-venous O2 difference (a-vO2 difference) derived from Q̇c and V̇O2 were assessed during exercise. Breath-by-breath O2 uptake was measured continuously throughout submaximal exercise, and V̇O2 kinetics was quantified as mean response time (MRT).

Results

HFpEF patients had markedly slowed V̇O2 kinetics during submaximal exercise (MRT: control: 40.1±14.2, HFpEF: 65.4±27.7 s; p<0.002), despite no relative impairment in submaximal cardiac output (Q̇c: control: 8.6±1.7, HFpEF: 9.7±2.2 L/min; p=0.79). When stratified by MRT, HFpEF with an MRT ≥60 s demonstrated elevated Q̇c, and impaired peripheral oxygen extraction that was apparent during submaximal exercise compared with HFpEF with a MRT <60 s (submaximal a-vO2 difference: MRT <60 s: 9.7±2.1, MRT ≥60 s: 7.9±1.1 mL/100 mL; p=0.03).

Conclusion

HFpEF patients have slowed V̇O2 kinetics that are related to impaired peripheral oxygen utilisation. MRT can identify HFpEF patients with peripheral limitations to submaximal exercise capacity and may be a target for therapeutic intervention.

Left atrial compliance index predicts exercise capacity in patients with heart failure and preserved ejection fraction irrespective of right ventricular dysfunction

BACKGROUND AND AIM

Predictors of exercise capacity in heart failure (HF) with preserved ejection fraction (HFpEF) remain of difficult determination. The aim of this study was to identify predictors of exercise capacity in a group of patients with HFpEF and right ventricle (RV) dysfunction METHODS: In 143 consecutive patients with HFpEF (age 62 ± 9 years, LV EF ≥45) and 41 controls, a complete echocardiographic study was performed. In addition to conventional measurements, LA compliance was calculated using the formula: [LAV max - LAV min/LAV min × 100]. Exercise capacity was assessed using the six-minute walking test (6-MWT). Tricuspid annular plane systolic excursion (TAPSE) < 1.7 cm was utilized to categorize patients with RV dysfunction (n = 40) from those with maintained RV function (n = 103).

RESULTS

Patients with RV dysfunction were older (P = 0.002), had higher NYHA class (P = 0.001), higher LV mass index (P = 0.01), reduced septal and lateral MAPSE (all P < 0.001), enlarged LA (P = 0.001) impaired LA compliance index (P < 0.001) and exhibited a more compromised 6-MWT (P = 0.001). LA compliance index correlated more closely with 6-MWT (r = 0.51, P < 0.001) compared with the other LA indices (AP diameter, transverse diameter and volume indexed; r = -0.30, r = -0.35 and r = -0.38, respectively). In multivariate analysis, LA compliance index <60% was 88% sensitive and 61% specific (AUC 0.80, CI = 0.67-0.92 P = 0.001) in predicting exercise capacity.

CONCLUSION

An impairment in LA compliance was profound in patients with HFpEF and RV dysfunction and seems to be most powerful independent predictor of limited exercise capacity.

The Added Value of Exercise Stress Echocardiography in Patients With Heart Failure

Doppler echocardiography can provide reliable and repeatable measures of cardiac index (CI), whereas lung ultrasound (LUS) represents a quantitative approach to assess pulmonary congestion. We tested the hypothesis that simultaneous assessment of CI and LUS during exercise stress echocardiography (ESE) may define heart failure (HF) outpatients with different risk of adverse outcome. Standard transthoracic echocardiography and LUS (B-lines) evaluation were assessed during semisupine ESE. CI and B-lines were measured at baseline and peak exercise. Resting plasma B-type natriuretic peptide levels were also evaluated. We enrolled 105 HF patients (87 males; age 62 ± 11 years; New York Heart Association class I to III) with reduced left ventricular ejection fraction (30 ± 7%). Patients were classified into 4 profiles: (1) peak CI ≥4.0 l/min/m² and peak B-lines <15 (no evidence of congestion or hypoperfusion, n = 47); (2) peak CI ≥4.0 l/min/m² and peak B-lines ≥15 (congestion with adequate perfusion, n = 23); (3) peak CI <4.0 l/min/m² and peak B-lines <15 (hypoperfusion without congestion, n = 13); and (4) peak CI <4.0 l/min/m² and peak B-lines ≥15 (congestion and hypoperfusion, n = 22). There were 21 cardiovascular deaths and 18 hospitalizations for worsening HF during a median follow-up of 29 months. Multivariate predictors of the combined end point were peak hemodynamic profiles (hazard ratio [HR] 1.62, 95% confidence interval [CI] 1.19 to 2.21; p = 0.002), B-type natriuretic peptide (HR 1.00, 95% CI 1.00 to 1.01; p = 0.001), and rest E/e' (HR 1.09, 95% CI 1.03 to 1.15; p = 0.002). Survival analysis showed a worse survival in patients with ESE-derived D profile, followed by patients with C, B, and A profile (log-rank: chi-square = 40.5; p <0.0001). In conclusion, dual evaluation of CI and LUS during ESE is useful for risk stratification of HF patients with reduced ejection fraction. Evidence of pulmonary congestion and low CI at peak ESE identifies a subgroup with a very high risk of adverse outcome.

Central and Peripheral Determinants of Exercise Capacity in Heart Failure Patients With Preserved Ejection Fraction

OBJECTIVES

This study sought to discern which central (e.g., heart rate, stroke volume [SV], filling pressure) and peripheral factors (e.g., oxygen use by skeletal muscle, body mass index [BMI]) during exercise were most strongly associated with the presence of heart failure and preserved ejection fraction (HFpEF) as compared with healthy control subjects exercising at the same workload.

BACKGROUND

The underlying mechanisms limiting exercise capacity in patients with HFpEF are not fully understood.

METHODS

In patients with HFpEF (n = 108), the hemodynamic response at peak exercise was measured using right-sided heart catheterization and was compared with that in healthy control subjects (n = 42) at matched workloads to reveal hemodynamic differences that were not attributable to the workload performed. The patients studied were prospectively included in the REDUCE-LAP HF (Reduce Elevated Left Atrial Pressure in Patients With Heart Failure) trials and HemReX (Effect of Age on the Hemodynamic Response During Rest and Exercise in Healthy Humans) study. Univariable and multivariable logistic regression models were used to analyze variables associated with HFpEF versus control subjects.

RESULTS

Compared with healthy control subjects, pulmonary capillary wedge pressure (PCWP) and SV were the only independent hemodynamic variables that were associated with HFpEF, a finding explaining 66% (p < 0.0001) of the difference between the groups. When relevant baseline characteristics were added to the base model, only BMI emerged as an additional independent variable, in total explaining of 90% of the differences between groups (p < 0.0001): PCWP (47%), BMI (31%), and SV (12%).

CONCLUSIONS

The study identified 3 key variables (PCWP, BMI, and SV) that independently correlate with the presence of patients with HFpEF compared with healthy control subjects exercising at the same workload. Therapies that decrease left-sided heart filling pressures could improve exercise capacity and possibly prognosis.

Higher cardiorespiratory fitness predicts long-term survival in patients with heart failure and preserved ejection fraction: the Henry Ford Exercise Testing (FIT) Project

INTRODUCTION

Higher cardiorespiratory fitness (CRF) is associated with improved exercise capacity and quality of life in heart failure with preserved ejection fraction (HFpEF), but there are no large studies evaluating the association of HFpEF, CRF, and long-term survival. We therefore aimed to determine the association between CRF and all-cause mortality, in patients with HFpEF.

MATERIAL AND METHODS

In the Henry Ford Exercise Testing (FIT) Project, 167 patients had baseline HFpEF, defined as a clinical diagnosis of heart failure with ejection fraction ≥ 50% on echocardiogram. The CRF was estimated from the peak workload (in METs) from a clinician-referred treadmill stress test and categorized as poor (1-4 METs), intermediate (5-6 METs), and moderate-high (≥ 7 METs). Additional analyses assessing the effect of HFpEF and CRF on mortality were also conducted, matching HFpEF patients to non-HFpEF patients using propensity scores.

RESULTS

Mean age was 64 ±13 years, with 55% women, and 46% Black. Over a median follow-up of 9.7 (5.2-18.9) years, there were 103 deaths. In fully adjusted models, moderate-high CRF was associated with 63% lower mortality risk (HR = 0.37, 95% CI: 0.18-0.73) compared to the poor-CRF group. In the propensity-matched cohort, HFpEF was associated with a HR of 2.3 (95% CI: 1.7-3.2) for mortality compared to non-HFpEF patients, which was attenuated to 1.8 (95% CI: 1.3-2.5) after adjusting for CRF.

CONCLUSIONS

Moderate-high CRF in patients with HFpEF is associated with improved survival, and differences in CRF partly explain the intrinsic risk of HFpEF. Randomized trials of interventions aimed at improving CRF in HFpEF are needed.

Effects of heavy-intensity priming exercise on pulmonary oxygen uptake kinetics and muscle oxygenation in heart failure with preserved ejection fraction

Exercise intolerance is a hallmark feature in heart failure with preserved ejection fraction (HFpEF). Prior heavy exercise ("priming exercise") speeds pulmonary oxygen uptake (V̇o_2p) kinetics in older adults through increased muscle oxygen delivery and/or alterations in mitochondrial metabolic activity. We tested the hypothesis that priming exercise would speed V̇o_2p on-kinetics in patients with HFpEF because of acute improvements in muscle oxygen delivery. Seven patients with HFpEF performed three bouts of two exercise transitions: MOD1, rest to 4-min moderate-intensity cycling and MOD2, MOD1 preceded by heavy-intensity cycling. V̇o_2p, heart rate (HR), total peripheral resistance (TPR), and vastus lateralis tissue oxygenation index (TOI; near-infrared spectroscopy) were measured, interpolated, time-aligned, and averaged. V̇o_2p and HR were monoexponentially curve-fitted. TPR and TOI levels were analyzed as repeated measures between pretransition baseline, minimum value, and steady state. Significance was P < 0.05. Time constant (τ; tau) V̇o_2p (MOD1 49 ± 16 s) was significantly faster after priming (41 ± 14 s; P = 0.002), and the effective HR τ was slower following priming (41 ± 27 vs. 51 ± 32 s; P = 0.025). TPR in both conditions decreased from baseline to minimum TPR ( P < 0.001), increased from minimum to steady state ( P = 0.041) but remained below baseline throughout ( P = 0.001). Priming increased baseline ( P = 0.003) and minimum TOI ( P = 0.002) and decreased the TOI muscle deoxygenation overshoot ( P = 0.041). Priming may speed the slow V̇o_2p on-kinetics in HFpEF and increase muscle oxygen delivery (TOI) at the onset of and throughout exercise. Microvascular muscle oxygen delivery may limit exercise tolerance in HFpEF.

Predictive Factors of Postoperative Blood Pressure Abnormalities Following a Minor-to-Moderate Surgery

Myocardial ischemic events after non-cardiac surgery is still a serious problem, especially in older, high-risk patients. However, the prevalence and risk factors of blood pressure (BP) abnormalities, which may possibly lead to myocardial ischemic attack, have not been reported. Our aim is to elucidate predictive factors of postoperative BP abnormalities following a minor-to-moderate surgery, employing preoperative left ventricular diastolic function. Patients who underwent cardiac echocardiogram examination and received oral and maxillofacial surgery under general anesthesia were enrolled. The echocardiographic parameters of diastolic function were compared between patients who had postoperative BP abnormalities (hypertension-systolic blood pressure [SBP] ≥ 170 mmHg-or hypotension-SBP < 80 mmHg-episode) that required therapeutic interventions until 7 days after surgery and those who had no BP abnormalities. Of the 173 patients analyzed, 25 (14.4%) had BP abnormalities. BP abnormalities patients were older, having a larger proportion of diabetes mellitus, lower E/A ratio and e', and larger E/e' and left atrial dimension than those without BP abnormalities. Subanalyses revealed that the independent risk factors responsible for hypertension episodes (14 patients) were the mean e' (odd ratio [OR]: 0.434; 95% confidence interval [CI]: 0.229-0.824), diabetes mellitus (OR: 5.018; 95% CI: 1.030-24.436), SBP at hospitalization (OR: 1.099; 95% CI: 1.036-1.165), and operation time (hour; OR: 1.326; 95%CI: 1.109-1.586), while hypotension episodes (11 patients) were associated solely with operation time (OR: 1.206; 95% CI: 1.046-1.391). In conclusion, left ventricular diastolic dysfunction, increased insulin resistance, boosted SBP at hospitalization, and prolonged operation should be taken into consideration as risk factors of postoperative BP abnormalities, especially hypertension, following minor-to-moderate surgery.

Aluminum: A potentially toxic metal with dose-dependent effects on cardiac bioaccumulation, mineral distribution, DNA oxidation and microstructural remodeling

Large amounts of aluminum (Al) are found in wastewater from industrial bauxite mining, which is often responsible for the contamination of drinking water sources in urban and rural communities. Although this metal exhibits broad environmental distribution, its cardiac repercussions are poorly understood, making it difficult to establish diagnostic criteria in cases of Al intoxication. In the absence of clinical data, we used a preclinical model to investigate the impact of Al exposure on heart bioaccumulation, molecular oxidation, micromineral distribution, structural and ultrastructural remodeling of the cardiac tissue. Male Wistar rats were equally randomized into five groups: G1 = distilled water; and G2 to G5 = 0.02, 0.1, 50, and 200 mg/kg aluminum solution, respectively. After 120 days, the hearts were collected and subjected to mineral microanalysis, immunoenzymatic detection of 8-OHdG, as well as bright field, polarizing, scanning and transmission electron microscopy to estimate the extent of the cardiac remodeling and cardiomyocytes ultrastructure. Long-term Al exposure induced dose-dependent bioaccumulation, micromineral imbalance, genomic DNA oxidation, structural and ultrastructural abnormalities of the cardiac tissue, resulting in extensive parenchymal loss, stromal expansion, diffuse inflammatory infiltrate, increased glycoconjugate and collagen deposition, subversion and collapse of the collagen network, reduced myocardial vascularization index, mitochondrial swelling, sarcomere disorganization, myofilament dissociation, and fragmentation in cardiomyocytes. Our findings indicated that the heart was sensitive to Al-mediated toxicity, especially in animals treated with the three highest doses of Al. In response to Al-induced loss of the parenchyma, heart stroma exhibited a reactive and compensatory expansion, which, in combination with the increased distribution of thick myofibrils and degenerated mitochondria in cardiomyocytes, provides morphological evidence that cardiac tissue adaptations are not enough to adjust the relationships between the parenchyma and stroma until a steady state is reached, resulting in continuous pathological remodeling potentially associated with Al-induced proinflammatory and pro-oxidant events.

Left atrial remodelling may predict exercise capacity in obstructive sleep apnoea patients

BACKGROUND

Left atrial volume (LAV) and LA deformation has been proposed as a good marker of exercise performance in patients with diastolic dysfunction (DD). As DD is more prevalent in obstructive sleep apnoea (OSA) we aimed to evaluate the influence of LAV and LA deformation parameters on exercise performance in varying severity of OSA.

MATERIALS AND METHODS

OSA was diagnosed after polysomnography. Fifty-five OSA patients were enrolled in the study. OSA patients were divided into two groups with apnoea-hypopna-index (AHI) > 30 and <30. LAV was calculated. LA strain and LA strain rates were assessed with speckle tracking echocardiography (STE). Exercise capacity was evaluated by treadmill exercise test.

RESULTS

MET values were lower in group II compared to group I (p < .05). Echocardiographic findings: Comparison within groups: In both groups E/E', LA stain, LA strain rate S and LA strain rate E were higher after exercise than before (p < .05). In group I LA strain rate A was higher after exercise than before (p < .05). Comparison between groups: LA strain, LA strain rate S, LA strain rate E and LA strain rate A were lower and E/E' and LAVI were higher in group II compared to group I before and after exercise (p < .05). Correlation with METs: AHI, LVEDV, E/E' and LAVI were negatively and LA strain was positively correlated with METs (p < .05).

CONCLUSIONS

Left ventricular diastolic dysfunction is more prevalent in severe OSA and is associated with impaired exercise performance. Additionally, LA remodelling may predict exercise capacity in this subgroup of patients.

Iron deficiency in patients with heart failure with preserved ejection fraction and its association with reduced exercise capacity, muscle strength and quality of life

BACKGROUND

The prevalence of iron deficiency (ID) in outpatients with heart failure with preserved ejection fraction (HFpEF) and its relation to exercise capacity and quality of life (QoL) is unknown.

METHODS

190 symptomatic outpatients with HFpEF (LVEF 58 ± 7%; age 71 ± 9 years; NYHA 2.4 ± 0.5; BMI 31 ± 6 kg/m²) were enrolled as part of SICA-HF in Germany, England and Slovenia. ID was defined as ferritin < 100 or 100-299 µg/L with transferrin saturation (TSAT) < 20%. Anemia was defined as Hb < 13 g/dL in men, < 12 g/dL in women. Low ferritin-ID was defined as ferritin < 100 µg/L. Patients were divided into 3 groups according to E/e' at echocardiography: E/e' ≤ 8; E/e' 9-14; E/e' ≥ 15. All patients underwent echocardiography, cardiopulmonary exercise test (CPX), 6-min walk test (6-MWT), and QoL assessment using the EQ5D questionnaire.

RESULTS

Overall, 111 patients (58.4%) showed ID with 89 having low ferritin-ID (46.84%). 78 (41.1%) patients had isolated ID without anemia and 54 patients showed anemia (28.4%). ID was more prevalent in patients with more severe diastolic dysfunction: E/e' ≤ 8: 44.8% vs. E/e': 9-14: 53.2% vs. E/e' ≥ 15: 86.5% (p = 0.0004). Patients with ID performed worse during the 6MWT (420 ± 137 vs. 344 ± 124 m; p = 0.008) and had worse exercise time in CPX (645 ± 168 vs. 538 ± 178 s, p = 0.03). Patients with low ferritin-ID had lower QoL compared to those without ID (p = 0.03).

CONCLUSION

ID is a frequent co-morbidity in HFpEF and is associated with reduced exercise capacity and QoL. Its prevalence increases with increasing severity of diastolic dysfunction.

Diastolic stress echocardiography: from basic principles to clinical applications

Heart failure with preserved ejection fraction (HFpEF) looms as a major public heart challenge with increasing prevalence due to an ageing population. Diagnosis can be challenging due to non-specific symptomatology, low natriuretic peptide levels and equivocal diastology on resting echocardiography. Diastolic stress echocardiography represents a non-invasive option to refining the diagnosis in this subset of patients. Diastolic responses to exercise are most commonly measured with a non-invasive measure of left ventricular filling pressures (LVFP) estimated by the ratio of the early mitral inflow wave to early diastolic tissue velocity (E/e' ratio). This is measured pre- and post-exercise , and is highly feasible. An elevation of exercise E/e' >15 is classified as an abnormal response as per current guidelines. An alternative measure of exercise-related diastolic performance, the Diastolic Functional Reserve Index has also been proposed, but has not been as well studied as exercise E/e'. A number of studies have validated exercise E/e' as a measure of LVFP against invasively measured LVFP using simultaneous echocardiography-catheterisation studies. The independent prognostic value of exercise E/e' has also been well delineated in a number of studies. While diastolic stress echocardiography can be considered for all patients with suspected HFpEF, it is of particular value in patients with normal or equivocal diastolic indices on resting echocardiography.

Determinants of exercise intolerance in heart failure with preserved ejection fraction: A systematic review and meta-analysis

BACKGROUND

Severe exercise intolerance (EI), demonstrated by impaired peak oxygen consumption, intrinsically characterizes heart failure with preserved ejection fraction (HFpEF). Controversy exists on the determinants of EI in patients with HFpEF according to case-control studies. The purpose of this study is to systematically review and clarify the main (Fick) determinants of EI in HFpEF.

METHODS

We conducted a systematic search of MEDLINE, Scopus and Web of Science since their inceptions until January 2017 for articles assessing peak cardiac output and/or arteriovenous oxygen difference (a-vO_2diffpeak) with incremental exercise in patients diagnosed with HFpEF and age-matched control individuals. Meta-analyses were performed to determine the standardized mean difference (SMD) in peak cardiac index (CI_peak) and a-vO_2diffpeak between HFpEF and control groups. Subgroup and meta-regression analyses were used to evaluate potential moderating factors.

RESULTS

Ten studies were included after systematic review, comprising a total of 213 HFpEF patients and 179 age-matched control individuals (mean age=51-73years). After data pooling, CI_peak (n=392, SMD=-1.42; P<0.001) and a-vO_2diffpeak (n=228, SMD=-0.52; P=0.002) were impaired in HFpEF patients. In subgroup analyses, a-vO_2diffpeak was reduced in HFpEF versus healthy individuals (n=114, SMD=-0.85; P<0.001) but not compared with control patients without heart failure (n=92, SMD=-0.12; P=0.57). The SMD in a-vO_2diffpeak was negatively associated with age (B=-0.05, P=0.046), difference in % females (B=-0.01, P=0.026) and prevalence of hypertension (B=-0.01, P=0.015) between HFpEF and control groups.

CONCLUSIONS

HFpEF is associated with a predominant impairment of CI_peak, accompanied by sex- and comorbidity-dependent reduced oxygen extraction at peak exercise.

Reversing the Cardiac Effects of Sedentary Aging in Middle Age-A Randomized Controlled Trial: Implications For Heart Failure Prevention

BACKGROUND

Poor fitness in middle age is a risk factor for heart failure, particularly heart failure with a preserved ejection fraction. The development of heart failure with a preserved ejection fraction is likely mediated through increased left ventricular (LV) stiffness, a consequence of sedentary aging. In a prospective, parallel group, randomized controlled trial, we examined the effect of 2 years of supervised high-intensity exercise training on LV stiffness.

METHODS

Sixty-one (48% male) healthy, sedentary, middle-aged participants (53±5 years) were randomly assigned to either 2 years of exercise training (n=34) or attention control (control; n=27). Right heart catheterization and 3-dimensional echocardiography were performed with preload manipulations to define LV end-diastolic pressure-volume relationships and Frank-Starling curves. LV stiffness was calculated by curve fit of the diastolic pressure-volume curve. Maximal oxygen uptake (Vo₂max) was measured to quantify changes in fitness.

RESULTS

Fifty-three participants completed the study. Adherence to prescribed exercise sessions was 88±11%. Vo₂max increased by 18% (exercise training: pre 29.0±4.8 to post 34.4±6.4; control: pre 29.5±5.3 to post 28.7±5.4, group×time P<0.001) and LV stiffness was reduced (right/downward shift in the end-diastolic pressure-volume relationships; preexercise training stiffness constant 0.072±0.037 to postexercise training 0.051±0.0268, P=0.0018), whereas there was no change in controls (group×time P<0.001; pre stiffness constant 0.0635±0.026 to post 0.062±0.031, P=0.83). Exercise increased LV end-diastolic volume (group×time P<0.001), whereas pulmonary capillary wedge pressure was unchanged, providing greater stroke volume for any given filling pressure (loading×group×time P=0.007).

CONCLUSIONS

In previously sedentary healthy middle-aged adults, 2 years of exercise training improved maximal oxygen uptake and decreased cardiac stiffness. Regular exercise training may provide protection against the future risk of heart failure with a preserved ejection fraction by preventing the increase in cardiac stiffness attributable to sedentary aging.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02039154.

Shortness of breath in clinical practice: A case for left atrial function and exercise stress testing for a comprehensive diastolic heart failure workup

The symptom cluster of shortness of breath (SOB) contributes significantly to the outpatient workload of cardiology services. The workup of these patients includes blood chemistry and biomarkers, imaging and functional testing of the heart and lungs. A diagnosis of diastolic heart failure is inferred through the exclusion of systolic abnormalities, a normal pulmonary function test and normal hemoglobin, coupled with diastolic abnormalities on echocardiography. Differentiating confounders such as obesity or deconditioning in a patient with diastolic abnormalities is difficult. While the most recent guidelines provide more avenues for diagnosis, such as incorporating the left atrial size, little emphasis is given to understanding left atrial function, which contributes to at least 25% of diastolic left ventricular filling; additionally, exercise stress testing to elicit symptoms and test the dynamics of diastolic parameters, especially when access to the "gold standard" invasive tests is lacking, presents clinical translational gaps. It is thus important in diastolic heart failure work up to understand left atrial mechanics and the role of exercise testing to build a comprehensive argument for the diagnosis of diastolic heart failure in a patient presenting with SOB.

Oxygen uptake on-kinetics during six-minute walk test predicts short-term outcomes after off-pump coronary artery bypass surgery

PURPOSE

We aimed to investigate the ability of oxygen uptake kinetics to predict short-term outcomes after off-pump coronary artery bypass grafting.

METHODS

Fifty-two patients aged 60.9 ± 7.8 years waiting for off-pump coronary artery bypass surgery were evaluated. The 6-min walk test distance was performed pre-operatively, while simultaneously using a portable cardiopulmonary testing device. The transition of oxygen uptake kinetics from rest to exercise was recorded to calculate oxygen uptake kinetics fitting a monoexponential regression model. Oxygen uptake at steady state, constant time, and mean response time corrected by work rate were analysed. Short-term clinical outcomes were evaluated during the early post-operative of off-pump coronary artery bypass surgery.

RESULTS

Multivariate analysis showed body mass index, surgery time, and mean response time corrected by work rate as independent predictors for short-term outcomes. The optimal mean response time corrected by work rate cut-off to estimate short-term clinical outcomes was 1.51 × 10^-3 min²/ml. Patients with slower mean response time corrected by work rate demonstrated higher rates of hypertension, diabetes, EuroSCOREII, left ventricular dysfunction, and impaired 6-min walk test parameters. The per cent-predicted distance threshold of 66% in the pre-operative was associated with delayed oxygen uptake kinetics.

CONCLUSIONS

Pre-operative oxygen uptake kinetics during 6-min walk test predicts short-term clinical outcomes after off-pump coronary artery bypass surgery. From a clinically applicable perspective, a threshold of 66% of pre-operative predicted 6-min walk test distance indicated slower kinetics, which leads to longer intensive care unit and post-surgery hospital length of stay. Implications for rehabilitation Coronary artery bypass grafting is a treatment aimed to improve expectancy of life and prevent disability due to the disease progression; The use of pre-operative submaximal functional capacity test enabled the identification of patients with high risk of complications, where patients with delayed oxygen uptake kinetics exhibited worse short-term outcomes; Our findings suggest the importance of the rehabilitation in the pre-operative in order to "pre-habilitate" the patients to the surgical procedure; Faster oxygen uptake on-kinetics could be achieved by improving the oxidative capacity of muscles and cardiovascular conditioning through rehabilitation, adding better results following cardiac surgery.

CXL-1020, a Novel Nitroxyl (HNO) Prodrug, Is More Effective than Milrinone in Models of Diastolic Dysfunction-A Cardiovascular Therapeutic: An Efficacy and Safety Study in the Rat

The nitroxyl (HNO) prodrug, CXL-1020, induces vasorelaxation and improves cardiac function in canine models and patients with systolic heart failure (HF). HNO's unique mechanism of action may be applicable to a broader subset of cardiac patients. This study investigated the load-independent safety and efficacy of CXL-1020 in two rodent (rat) models of diastolic heart failure and explored potential drug interactions with common HF background therapies. In vivo left-ventricular hemodynamics/pressure-volume relationships assessed before/during a 30 min IV infusion of CXL-1020 demonstrated acute load-independent positive inotropic, lusitropic, and vasodilatory effects in normal rats. In rats with only diastolic dysfunction due to bilateral renal wrapping (RW) or pronounced diastolic and mild systolic dysfunction due to 4 weeks of chronic isoproterenol exposure (ISO), CXL-1020 attenuated the elevated LV filling pressures, improved the end diastolic pressure volume relationship, and accelerated relaxation. CXL-1020 facilitated Ca²⁺ re-uptake and enhanced myocyte relaxation in isolated cardiomyocytes from ISO rats. Compared to milrinone, CXL-1020 more effectively improved Ca²⁺ reuptake in ISO rats without concomitant chronotropy, and did not enhance Ca²⁺ entry via L-type Ca²⁺ channels nor increase myocardial arrhythmias/ectopic activity. Acute-therapy with CXL-1020 improved ventricular relaxation and Ca²⁺ cycling, in the setting of chronic induced diastolic dysfunction. CXL-1020's lusitropic effects were greater than those seen with the cAMP-dependent agent milrinone, and unlike milrinone it did not produce chronotropy or increased ectopy. HNO is a promising new potential therapy for both systolic and diastolic heart failure.